There is an increasing demand of multi-speed operation of electric motors used in automotive applications, especially in engine cooling applications where lower fan speed operation is required to reduce power consumption and the noise pollution during lower or normal engine load conditions. The high fan speed from the engine cooling unit is required for maximum, worst case engine load conditions. There are a variety of different configurations and methods available on the market for two or multi speed operation of electric motors.
For Permanent Magnet Direct Current Brush Motors (PMDC BM) historically lower speeds (multiple speed operation) have been achieved by the following methods:                Adding a resistor in series with the motor        Switching out brushes        Dual armature winding with dual commutator        Adding an additional 3rd brush (short out coils)        External or internal electronic control comprised of but not limited to:                    SSR, (Solid State Relays), Linear control, PWM, (Pulse Width Modulation), Variable flux coils combined with permanent magnets                        
As is evident from the above list, there are many solutions available for varying the speed of an electric motor. However, most of these solutions, which are more economically feasible, are limited to two or maximum three speed operations. The higher technology products such as the PWM controllers are truly capable of operating at variable/multi-speeds. However, the complexity and cost of such controllers are significantly higher than the lower cost two or three speed conventional solutions.
Although the PWM controllers can provide variable/multi speed control for such as the engine cooling unit, most of the auto manufacturers are only using (programming into the ECU) four load points. Some auto manufacturers and engine cooling pack suppliers expressed interest for lower cost four-speed engine cooling modules.
Therefore, there is a need to provide a new, low cost solution to achieve four-speed operation of an electric motor used in automotive applications such as an engine cooling module.